RTC woes

Hi:

I'm new to the list.  I have an e500-based embedded Linux system running a
2.6.22 kernel.  I have a PCF8563T i2c based RTC chip attached to the PPC i2c
bus.  In my kernel config file I have selected CONFIG_RTC_INTF_DEV=y and
CONFIG_RTC_DRV_PCF8563=y.  I do a mknod  for /dev/rtc as c 10 135 (standard
Linux) and link /dev/rtc0 to it.

 

When I boot, get the following message:

 

drivers/rtc/hctosys.c: unable to open rtc device (rtc0)

 

and, of course I cannot access /dev/rtc after booting.  I can, however, talk
to the rtc if I use /dev/i2c and a generic i2c read and write utility.

 

When I look in /proc/devices, I see that rtc has taken major number 254
which puzzles me. RTC should not need a dynamic major number, right?  I have
perused the drivers in linux/drivers/rtc and don't find any of them calling
register_chrdev() to get a dynamic major number.  So here are my questions:

 

1)       Shouldn't rtc automagically use major/minor 10/135?

2)       How can I find where in the source it asks for a dynamic major
number?

3)       Does the PPC have some quirks regarding i2c operation that are at
the root of this problem?

 

BYW, I tried making the rtc device file as c 254 0 to match what's in
/proc/devices and that gives me the same bejavior.

 

Thanks in advance for any help you can offer.

 

Marc

 

Marc LeFevre schrieb:

I’m new to the list.

Welcome! :-)

 > I have an e500-based embedded Linux system running

a 2.6.22 kernel.  I have a PCF8563T i2c based RTC chip attached to the 
PPC i2c bus.  In my kernel config file I have selected 
CONFIG_RTC_INTF_DEV=y and CONFIG_RTC_DRV_PCF8563=y.  I do a mknod  for 
/dev/rtc as c 10 135 (standard Linux) and link /dev/rtc0 to it.

  > When I boot, get the following message:

drivers/rtc/hctosys.c: unable to open rtc device (rtc0)

2.6.22.x and 2.6.23.x i2c rtc code was quite messy around PCF8563.

3)       Does the PPC have some quirks regarding i2c operation that are 
at the root of this problem?

The RTC subsystem was improved quite a bit lately. Try 2.6.24' powerpc
architecture with a proper device tree instead. It works over here on
mpc8540 / mpc8548 whereas the older ones were just a waste of time.

Regards,

Clemens